Organic gardening relies on the addition of organic materials such as compost, manure, and mulch to enrich the soil rather than using commercial fertilizers and chemicals. Earthworms may also be added to the soil to aerate and further condition it. Gardening organically also consists of using natural pesticides and pest deterring herbs and plants rather than chemical poisons to rid the garden of unwanted bugs. Often natural predators, such as ladybugs and preying mantises are introduced to eliminate the pests.